Method and device relating to absorption refrigerating apparatus



Oct. 11, 1949. s. M. BAcKsTRdM 2,484,669

v METHOD AND DEVICE RELATING TO ABSORPTION REFRIGERATING APPARATUS Filed April 7, 1942 INVENTOR A44 ATTORNEY Patented Oct. 11, 1949 METHOD AND DEVICE RELATING TO ABSORPTION REFRIGERATING AP- PARATUS Sigurd Mattias Biickstriim, Stockholm, Sweden, asslgnor to Aktiebolaget Elektrolux, Stockholm, Sweden, a corporation of Sweden Application April 7, 1942, Serial No. 437,998 In Sweden April 22, 1941 31 Claims.

The present invention relates to a method of and apparatus for regulating the cooling effect of an hermetically closed, air cooled, continuous absorption refrigerating system of the type using an inert pressure equalizing gas to maintain the same total pressure throughout the system.

The invention is characterized chiefly in that condensate produced only during abnormal working conditions is used to form liquid columns for causing a pressure differential between different parts of the apparatus and utilizing the pressure diiferential as an impulse or controlling force. According to the invention use is made of condensate produced in the so-called pressure vessel for building up the water columns. The invention further relates to a method and apparatus utilizing the controlling force for regulating the operation of the apparatus by controlling the flow of a fluid in the system.

The invention will become more apparent from the following description of the drawings. In the drawings:

Fig. l is a diagrammatical view of an absorption refrigeration system incorporating apparatus for regulating the cooling effect of the evaporator, and.

Fig. 2 is a sectional view of one of the valves in the apparatus for controlling the operation of the system.

In Fig. 1, i designates the boiler of the refrigerating apparatus and I2 the vapor conduit extending from the boiler. Said conduit l2 opens into the upper part of a leveling vessel i3 from which the vapor is led through an air cooled rectifier Hi to an air cooled condenser I? provided with cooling fins. The condensate produced in the condenser ii is supplied to a leveling vessel I5 from thebottom of. which the refrigerant flows through a conduit H into the upper end of an evaporator in the form of a tubular coil. The upper section H. of the evaporator is provided with fins for increasing the heat transfer surface and is arranged for space cooling whereas the lower section it is arranged for low temperature. cooling.

Further, 2B designates a so-called pressure vessel which compensates for variations in the pressure of the working media caused by variations in the temperature of the ambient air. At high air temperatures, all of therefrigerant vapor will not condense in the condenser l1 and will flow through a conduit 2| into the pressure vessel 20 and displace the inert gas therein. The conduit 2| opens into a small recess IS in the bottom of the pressure vessel 20. Two conduits 22 and 23 are connected at one of their ends to lower and upper parts of the pressure vessel 20 and the other ends of the conduits are connected to one leg of a U-tube 24. The other leg of the U-tube 24 is connected to a leveling vessel 25. The lower end of the leveling vessel 25 is connected through a U-tube 26 and conduit 21 to a reservoir 28 suitably arranged in a-refrigerator cabinet above the evaporator section l9 and the reservoir is provided with fins to adapt it for space cooling.

The leveling vessel 13 is connected by a conduit 30 with four valve vessels 3|, 32, 33 and 34 in the circulating system for the inert gas. The valve vessels 3| and 34 are connected by conduits 4| and 44, respectivehr, with the outer jacket of a gas heat exchanger 35. The valve vessels 32 and 33 are connected by conduits l2 and 43, respectively, with the inner tube of the gas heat exchanger 35. The valve vessels 3| and 32 are also connected to each other by an inverted U-tube 36, one leg of which extends into the vessel 32 on a level with the end of the tube 42 and the other leg of which extends into the vessel 3| and a float valve 31 in the vessel, as will be later more fully described, with its end positioned at a level somewhat higher than the tube end .42. The lower end of the evaporator section I8 is connected to the left leg of the U-tube 36. In a similar manner the valve vessels 33 and 34 communicate with each other through an inverted U-tube 38 and the vessel 33 is provided with a corresponding float valve 33. The right leg of the U-tube 33' is adapted to communicate with the upper end or the evaporator section It through the refrigerant reservoir 23. The end of the evaporator section. it, in fact, extends into a dome til arranged on the reservoir 28and the reservoir 28 is connected in the right leg of the U-tube 33 in such manner that the tube end 45 is located above the level of any liquid refrigerant in chamber 28 but below the end of the coil of evaporator section It in the dome.

The lower part of the gas heat exchanger is connected by conduits 5t and 5| to the absorber coil 52 and the absorber vessel 53, respectively. The inert gas separated from the refrigerant in the absorber 52 can flow into the upper end of the evaporator section i9 through the conduit 50, outer jacket of the heat exchanger 35, conduit B4 and U-tube 38, orto the lower end of the evaporator section I8 through the conduit 4| and U-tube 33. The gas rich in refrigerant is returned from the upper or lower ends of the evaporator to the absorber vessel 53 by way of.

the valve vessels or 33 and conduits 42 or 48, respectively, and then through the inner tube of the gas heat exchanger 35. Thus, the arrangement is such that when the valves 3| and 33 are closed the inert gas flows from the absorber into the upper section of the evaporator and passes through the evaporator in a direction of flow concurrent with the liquid refrigerant.

The liquid absorbent is circulated in a manner well known in the art with the solution weak in refrigerant flowing from the boiler in through a conduit 46, liquid heat exchanger 41 and conduit 48 to the absorber I2, and with the absorption solution rich in refrigerant flowing from the absorber vessel 53 through conduit 4!, liquid heat exchanger 4'! and a conduit 54 to the thermosiphon pump 55 of the boiler.

4 When the apparatus is started, condensate gradually collects in the leveling vessel i3 until the liquid level rises to the level oi the outlet end of the vapor tube 12. The liquid in the leveling vessel is flows through the conduit 80 to the valve vessels 3| to 34 which gradually nu with the liquid, the liquid level in the valve vessels ris to the same level as in the vessel it. The arrangement is such that at a low liquid level the valves 3'! and 39 are closed to provide a path of flow from the conduit 44 through the left leg of the U-tube 88 into the reservoir 28 and upper end of the evaporator section it and from the lower end of the evaporator section it through the left leg of the U-tube 38 to the conduit d2.

The refrigerant vapor from the boiler i0 flows from the vessel I! through the rectifier it to the condenser ll. Assuming the temperature of the cooling air to be relatively low, the capacity of the condenser is suflicient for complete condensation of all of the refrigerant vapor. The condensate flows through the leveling vessel is and the conduit I i into the upper section is of the evaporator arranged for space cooling purposes through which the condensate flows by gravity through both sections is and i8 and evaporates therein. Any unevaporated liquid refrigerant will drain from the evaporator section it through the left leg of the U-tube' 3Bto the valve vessel 32. The evaporation of liquid refrigerant in the evaporator produces a gas circulation in the same di= rection as the flow of refrigerant. When the concentration of refrigerant increases, the gas mixture becomes heavier and flows by way of the valve vessel 32 and the inner tube of the heat exchanger 35 into the absorber vessel 53 and thence into the absorber 52.

Under the conditions of operation assumed above, the pressur vessel contains mainly inert gas, for instance ydrogen, as the condenser is able to completely condense the generator vapors. The pressure vessel 20 is in communication through the conduits 22, 23, 24 and a conduit 5 with the inverted U-pipe 38, due to which the same pressure is maintained in the generator as in the absorber and the evaporator. Assuming now that the temperature of the cooling air in- The condensation of am-;

liquid column hto be produced in the conduit BC with a corresponding pressure rise in the pressure vessel 20. Consequently, the pressure in the pressure vessel 20, as well as in the generator II, will be higher than the pressure in the evaporator II and in the absorber 52 and the liquid will rise in the absorber vessel 53 from the level n to the level h. In order to assure control over these various pressure differences, a vent conduit 51 is connected between the pressure vessel 20 and the absorber 53 at a point located below the liquid level in the latter.

The increased pressure in the generator i0 depresses the liquid level therein by an amount h while the liquid level in the absorber 53 rises slightly to the level a The level in the vessel is is also depressed with a corresponding rise oi the level in the valve receptacles ei-td. 0n the drawing the original levels, that is to say, the level existing under normal conditions of operation, are dwignated by I, while the levels under the above described abnormal conditions are indicated by 11. Hence, the higher pressure in the pressure vessel 20 and generator ill also causes each of the liquid levels h h h. and h to change from the level I to the level II. The immediate efiect oi the rise in the liquid level in the valve vessels 32 and 34 is that the passage from the conduit 64 to the U-pipe 38 or from the U-pipe 36 to the conduit 42, respectively, is closed, so that the inert gas cannot continue to pass this way and consequently no longer flows through the evaporator in parallel flow with the liquid refrigerant. The rising of the liquid level in the valve receptacles 3i and 33, however, opens another path for the inert gas through the valve receptacle 3!, the U-pipe as and the lower end of the evaporator section It and from the evaporator reservoir 28 through theright leg of the U-pipe 38 and the valve receptacle as, that is to say, a path of flow through which the gas passes in a counter-current direction to the downward flowing cooling agent.

In order to make it possible to open the valves 8i and 33, they are, according to the invention, made inthe form of float valves, the construction of which is shown in Fig. 2. The ends of the U-pipes 88 and it are each provided with a flange or collar from which a valve body N is suspended. In the embodiment shown each valve body 6| consists of a cylinder in the upper end of which an opening is made having a diameter slightly larger than the diameter of the pipe as or 36, respectively. The bottom of the cylinder Si is formed of a plate 62 preferably made of wood. The cylinder 6! may suitably be provided with a drain opening 68. The float is so dimensioned that the buoyancy is suiiicient to raise the float upon a rise in the liquid level and in this manner open a path of flow for the gas. This open position is indicated in the drawing by dotted lines in Fig. 2. To prevent the float from rising too high, pawls 54 are provided. Otherwise the rise of the liquid level is limited by a drain conduit 65 (Fig. 1), preferably provided with a liquid seal, and connected to one of the connected valve receptacles and through which conduit any excess liquid is drained into the absorber.

The reversal of 'the direction of the circulating gas is quite complicated especially at the beginning of the reversing cycle. After the valves 3| and I2 have been closed the hydrogen enriched by refrigerant vapor cannot flow downwardly through the left leg of the U-tube 36 but instead the gas, after passing through the evaporator, will v the conduit rise therein. Before the enriched gas reaches the highest point in the U-tube 36 the column of gas therein will over-balance the column of gas in the evaporator 18, I9 to cause the gas to reverse its direction of flow and enter the reservoir or upper evaporator vessel 28. The enriched gas then will enter the overflow 45 and flow downwardly through the right leg of the U-tube 38. This reversal is further facilitated by liquid refrigerant flowing from the pressure vessel 20 through the conduit 21 into the upper evaporator vessel or reservoir 28 to enrich the hydrogen with refrigerant vapor whereby to increase its density and promote a flow downwardly through the right leg of the U-tube 38.

The heavy ammonia enriched gas seeks its outlet at the pipe end 45 before it reaches the outlet of the pipe in the dome 40. The enriched gas in the right arm of the U-pipe 38 consequently becomes so heavy that the circulation starts and gas flows down to vessel 33 and through conduit 43, heat exchanger 35 and conduit to the absorber and from there through conduit 50, heat exchanger 35, conduit 4| and U-pipe 36 to the lower part of the evaporator section IS. The ammonia which is not evaporated in the reservoir 28 is led through the conduit 66 to the evaporator l8, l9.

When the temperature .of the cooling air again drops, that is to say, when more favorable operating conditions occur, the condenser l1 gradually condenses the refrigerant vapor and creates a certain suction action which results in an emptying of the condensate in the conduit 56 and breaking the liquid seal 24, the contents thereof being sucked into the recess I6 and the conduit 2i. When this occurs different gas spaces in the system are no longer completely separated as is the case when the liquid column is produced in 56. The normal vent paths are opened in this way so that pressure equalization in the apparatus again becomes normal which, in turn, gradually lowers the liquid levels to the position indicated by I. The valves 3| and 33 are thereby closed and the valves 32 and 34 opened. By this method of regulating the temperature and temperature distribution in the evaporator of the refrigerator, the same cooling apparatus can easily be adjusted to varying loads and varying coolin air temperatures. It has been proven that at a high cooling air temperature counter-current flow of the gas and the liquid refrigerant in the evaporatorbrings about the best results, while at a low cooling air temperature counter-current flow brings about too low a temperature in the cooling box. At the same time the ice freezing capacity of the evaporator may become insufficient, due to the fact that with counter-current flow the essential evaporation takes place in the upper section of the evaporator so that the quantity of ammonia is not suflicient for an evaporation in the lowermost parts of the evaporator coil.

In view of the foregoing, it will now be understood that the arrangement accordin to Fig. 1 operates to a certain extent as a thermostat. As a matter of fact, the condenser ll operates not only as the condenser of the apparatus but also as a feeling member under the action of which variations in the cooling air temperature are converted to impulses for the valves 3 l-34. The pressure vessel acts in the same manner upon increase in load resulting from increase in temperature of cooling air. It is obviously of great advantage to be able to use the elements of the refrigeration system for transmitting impulses and to use an operating medium of the apparatus as a transmitting agent for these impulses.

It will be evident from the above description that refrigerant vapor in liquid phase is collected in the recess I6 of the pressure vessel 20 and in the liquid seal 24 upon increase in load. As previously explained, the condensation of rei'rigerant vapor in the pressure vessel 20 causes the liquid column k to be produced in the conduit 56. This in turn causes liquid columns to form in the system whereby the pressure in the pressure vessel 20 and generator III will be higher than the pressure in the evaporator l8 and absorber 52.

In accordance withthe principles of the invention, therefore, the condensate collected in the recess l6 and liquid seal 24 is utilized to produce liquid columns in the system which will build up a pressure differential between the gas spaces of different parts. Moreover, such pressure differential is utilized to modify the behavior of a fluid in the system. This is accomplished in the illustrated embodiment of the invention by employing the liquid columns built up in vessels 3!, 32, 33 and 34 to change the direction of flow of inert gas through the evaporator l8.

Although a single embodiment of the invention has been shown and described, it will be apparent to those skilled in the art that various modifications and changes may be made without departing from the true spirit and scope of the invention, as pointed out in the following claims.

I claim:

1. The method of controlling the temperature distribution in the cooling element of an absorption refrigeration system using an auxiliary pressure equalizing medium which comprises separating refrigerant vapor from an absorbent, liquefying the refrigerant vapor, flowing the liquid refrigerant in a predetermined path through the cooling element, flowing the auxiliary pressure equalizing medium through the cooling element in one direction to cause the refrigerant to evaporate at a relatively low temperature, absorbing the refrigerant vapor in the absorbent to separate the pressure equalizing medium therefrom, and reversing the direction of flow of the auxiliary pressure equalizing medium through the cooling element in accordance with a change in the temperature of the ambient air.

2. The method of controlling the temperature distribution in the cooling element of an absorption refrigeration system using an auxiliary pressure equalizing medium which comprises separating refrigerant vapor from an absorbent, liquefying the refrigerant vapor, flowing the liquid refrigerant in a predetermined path through the cooling element, flowing the auxiliary pressure equalizing medium through the cooling element in one direction to cause the refrigerant to evaporate at a relatively low temperature, absorbing the refrigerant vapor in the absorbent to separate the pressure equalizing medium therefrom, and reversing the direction of flow of the auxiliary pressure equalizing medium through the cooling element in accordance with a change in the load.

aceacec separating refrigerant vapor from an absorbent,

liqueiying the refrigerant vapor, flowing the liquid refrigerant in a predetermined path through thecpoling element, flowing the auxiliary pressure equalizing medium through the cooling element in one direction to cause the refrigerant to evaporate at a relatively low temperature, absorbing the refrigerant vapor in the absorbent to separate the pressure equalizing medium therefrom, and reversing the direction of flow of the auxiliary pressure equalizing medium through the cooling element in accordance with a change in the pressure in the system.

4. The method of controlling the temperature distribution in the cooling element of an absorption refrigeration system using an auxiliary pressure equalizing medium which comprises separating refrigerant vapor from an absorbent, liquefying the refrigerant vapor, flowing the liquid refrigerant in a predetermined path through the cooling element, flowing the auxiliary pressure equalizing medium through the cooling element in a direction concurrent with the liquid refriger ant, absorbing the refrigerant vapor in the absorbent to separate the pressure equalizing medium therefrom, and reversing the direction of flow of the auxiliary pressure equalizing medium through the cooling element inxesponse to a predetermined change in the temperature of the ambient air to cause the medium to flow in a direction countercurrent to th liquid refrigerant.

5. The method of controlling the temperature distribution in the cooling element of an absorption refrigeration system using an auxiliary pressure equalizing medium which comprises separating refrigerant vapor from an absorbent, liquefying the refrigerant vapor, flowing the liquid refrigerant in a predetermined path through the cooling element, flowing auxiliary pressure equalizing medium in a first path of flow concurrent with the liquid refrigerant in the cooling element and also in a second path of flow countercurrent to the liquid refrigerant, evaporating the liquid refrigerant in the presence of the auxiliary pressure equalizing medium to cause the refrigerant to evaporate at a relatively low temperature, ab-

sorbing the refrigerant vapor in the absorbent to separate the pressure equalizing medium therefrom, and shifting the flow of the auxiliary pressure equalizing medium from one to the other of its separate paths of flow in response to changes in pressure in the system.

6. The method of controlling the temperature 1 distribution in the cooling element of an absorption refrigeration system using an auxiliary pressure equalizing medium which comprises separating refrigerant vapor from an absorbent, condensing the refrigerant vapor by transferring heat to the-ambient air, flowing the liquid refrigerant in a predetermined path through the cooling ele- "ment, flowing the auxiliary pressure equalizing medium through the cooling element in one direction to cause the refrigerant to evaporate at a relatively low temperature, absorbing the refrigerant vapor in the absorbent to separate the pressure equalizing medium therefrom, and reversing the direction of flow of the pressure equalizing medium in response to a predetermined increase in the temperature of the ambient air.

7. The method of controlling the temperature distribution in the cooling element of an absorption refrigeration system using an auxiliary pressure equalizing medium which comprises separating refrigerant vapor from an absorbent, condensingthe refrigerant vapor at one place by transferducing a pressure differential in the system, and utilizing the pressure difierential in the system to reverse the direction of flow of the auxiliary pressure equalizing medium" through the cooling element.

8. The method of controlling the temperature distribution in thecooling element of an absorption refrigeration system using an auxiliary pressure equalizing medium which comprises separating refrigerant vapor from an absorbent, condensing the refrigerant vapor at one place during normal operation, flowing condensed refrigerant in a predetermined path through the cooling element, flowing the auxiliary pressure equalizing medium through the cooling element in a direction concurrent with the liquid refrigerant, evaporating the liquid refrigerant in the presence of the pressure equalizing medium, absorbing the refrig erant vapor in the absorbent to separate the pressure equalizing medium therefrom, condensing the refrigerant vapor at another place upon an abnormal increase in temperature of the ambient air, utilizing the condensate formed at the second place to form a liquid column for producing a pressure differential in the system, and utilizing the pressure differential in the system to reverse the direction of flow of the pressure equalizing medium through the cooling element to cause. it to flow in a direction countercurrent to the refrigerant;

9. In an absorption refrigeration system comprising a plurality of elements including an evaporator interconnected to provide a closed circuit for the circulation of a refrigerant, an absorbent, and an auxiliary pressure equalizing medium, and

mechanism in the circuit responsive to changes in the temperature of the ambient air for reversing the direction of flow of the pressure equalizing medium through the evaporator.

10. In an absorption refrigeration system comprising a plurality of elements including an evaporator interconnected to provide a closed circuit for the circulation of a refrigerant, an absorbent, and an auxiliary pressure equalizing medium, and

mechanism in the circuit responsive to changes in pressure in the system for reversing the direction of flow of the pressure equalizing medium through the evaporator.

, 11. An absorption refrigeration system of a type employing auxiliary pressure equalizing fluid and having a circuit for auxiliary fluid including an evaporator, a refrigerant liquefler connected to deliver liquid refrigerantto said evaporator, said cricuit providing alternative paths of flow each including said evaporator and so arranged that when one of said paths is in use auxiliary fluid flows in one direction through said evaporator and when the other of said paths is in use auxiliary fluid flows in another direction through said evaporator, and structure operative upon change in a condition affecting operation of the system to select the use of one or the other pressure equalizing medium to flow in one di- I rection through the evaporator and the other path causing the medium to flow in the opposite direction through the evaporaton'and' valves in the conduits for selecting the path and direction of flow of the pressure equalizing medium through the evaporator.

13. In an absorption refrigeration system comprising a plurality of elements including an evaporator, conduits connecting the elements to provide a closed circuit for the circulation of a. refrigl equalizing medium to flow through the evaporator in one direction and the other path causing 4 the medium to flow through the evaporator in the opposite direction, and valves operative upon change in a condition affecting operation of the system to close one of said paths and open the:

other of said paths and thereby control the direction of flow of the pressure equalizing medium in said evaporator.

17. In an absorption refrigeration system comprising a plurality of elements including an evaporator and an absorber, conduits interconnecting the elements to'provide a closed circuit for the circulation of a refrigerant and absorbent, said connecting conduits including main conduits leadng to and from the absorber to provide a single path of flow through the absorber, branch conduits connecting the main conduits to provide erant and absorbent and provide separate paths of flow for an auxiliary pressure equalizing medium, one of said paths causing the pressure equalizing medium to flow in one direction through the evaporator and the other path causing the medium to flow in the opposite direction through the evaporator, valves in the conduits for selecting the path and direction of flow of the pressure equalizing medium through the evaporator, and means responsive to changes in the temperature of the ambient air for operating the valves to close one path of iiow and open the other path of flow.

14. In an absorption refrigeration system comprising a plurality of elements including an evaporator, conduits interconnecting the elements to provide a closed circuit for the circulation of a refrigerant and absorbent and provide separate paths of flow for an auxiliary pressure equalizing medium, one of Said? paths causing the pressure equalizing medium to flow through the evaporator in a direction concurrent with the refrigerant and the other paths causing the medium to flow through the evaporator in a direction countercurrent to the refrigerant, and valves in the conduits for selecting the path and direction oi flow of the pressure equalizing medium through the evaporator.

15. in an absorption refrigeration system comprising a plurality of elements including an evaporator, conduits interconnecting the elements to provide a closed circuit for the circulation of a refrigerant and absorbent and provide separate paths of flow for an auxiliary pressure equalizing medium, one of said paths directing the pressure equalizing medium through the evaporator for flow concurrent with the refrigerant and the other path directing the medium through the evaporator for flow countercurrent to the refrigerant, valves in the conduits for selecting the path and direction of flow of the pressure equalizing medium through the evaporator, and means operative upon a change in a condition affecting oper-= ation of the system for operating the valves to close one path of flow and open the other path of flow.

16. In an absorption refrigeration system comprising a plurality of elements including an evaporator and an absorber, conduits interconnecting the elements to provide a closed circuit for the circulation of a refrigerant and absorbent, said connecting conduits providing a single path of flow for a pressure equalizing medium through the absorber and separate paths of flow to the evaporator, one of the paths causing the pressure separate paths of flow to the evaporator, one of .said paths causing'an auxiliary pressure equalizing medium to flow in one direction through the evaporator and the other path causing the medium to flow in the opposite direction through the evaporator, valves in the conduits, and a hydraulic circuit responsive to variations in pressure in the system for operating the valves to select the use of one or the other of said paths and thereby control the direction of flow in said evaporator.

18. In an absorption refrigeration system comprising a generator, a condenser, an evaporator, an absorber, a pressure vessel, conduits interconnecting the elements to provide a closed circuit for the circulation of a refrigerant and absorbent and provide separate paths of flow for an auxiliary tor, one of said paths of flow causing the auxiliary pressure equalizing medium to flow in one direction through the evaporator and the other path of flow causing the medium to flow in the opposite direction through the evaporator, said connecting conduit between the pressure vessel and evaporator providing a liquid trap to produce a pressure differential in the system upon an increase in the temperature of the ambient air, and mechanism responsive to the pressure difl'erential for selecting the path and the direction of flow of the auxiliary pressure equalizing medium through the evaporator.

19. In an absorption refrigeration system comprising a generator, a condenser, an evaporator, an absorber, a pressure vessel, conduits intercomnecting the elements 'to provide a closed circuit ior the circulation of a refrigerant and an absorbent and provide separate paths of flow for an auxiliary pressure equalizing medium to the evaporator, one of said paths causing the pressure equalizing medium to flow through the evaporator in a direction concurrent with the refrigerant and the other path of flow causing the medium to flow through the evaporator countercurrent to the refrigerant, a liquid trap in the conduit connecting the pressure vessel and evaporator for producing a pressure differential in the system upon an increase in the temperature of the ambient air, and valves operated by the pressure differential for selecting the path and direction of flow for the pressure equalizing medium through the evaporator. l

20. In an absorption refrigeration system comprising a generator, a condenser, an evaporator, an absorber, a pressure vessel, conduits interconnecting the elements to provide a closed circuit for the circulation of a refrigerant and an abcrbent and provide separate paths of flow for amuse ll an auxiliary pressure equalizing medium to the evaporator, one of said paths causing the pressure equalizing medium to flow through the evaporator in a direction concurrent with the refrigerant and the other path of flow causing the medium to flow through the evaporator in a direction countercurrent to the refrigerant, a liquid trap in the conduit connecting the pressure vessel and evaporator for producing a pressure differential in the system upon an increase in the temperature of the ambient air, valves for selecting the path and direction of flow of the pressure equalizing medium through the evaporator, and a hydraulic circuit rnsive to variations in the pressure differential in the system for operating the valves.

21. The method of controlling the operation of an absorption refrigeration system having a cooling element and utilizing a refrigerant, absorbent and an auxiliary pressure equalizing medium which comprises separating refrigerant vapor from an absorbent, condensing the. refrigerant at one place in the system by transferring heat to the ambient air, flowing condensed liquid refrigerant through the cooling element, flowing the auxiliary pressure equalizing medium through the cooling element to cause the refrigerant to vaporize at a relatively low temperature, flowing absorption solution to absorb the refrigerant vapor, condensing refrigerant vapor at another place in the system upon an increase in temperature of the ambient air, producing a liquid colunm from the condensate formed at the second place, completely separating different gas spaces in the system and establishing a pressure differential therebetween due to such liquid column, and changing the path of flow of onev of the fluids in the system due to such pressure diflerential.

22. The method of controlling, an absorption refrigeration system having a cooling element and utilizing a refrigerant, absorbent and an auxiliary pressure equalizing medium which comprises separating refrigerant vapor from an absorbent, condensing the refrigerant at one place in the system by transferring heat to the ambient air, flowing condensed liquid refrigerant through the cooling element, flowing the auxiliary pressure equalizing medium through the cooling element to cause the refrigerant to vaporize at a relatively low temperature, flowing absorption solution to absorb refrigerant vapor, condensing the refrigerant vapor at another place in the system upon an increase in temperature of the ambient air, producing a liquid column from the condensate formed at the second place, completely separating different gas spaces in the system and establishing a pressure'diilferential therebetween due to such liquid column, and changing the path of flow of the pressure equalizing medium in the system due to such pressure differential. 23. In the art of refrigeration with the aid of a system having a number of parts including an evaporator, an absorber and a generator interconnected for circulation of refrigerant and absorption solution and employing an inert gas for maintaining the same total pressure in such parts during normal operation of the system, the improvement which comprises collecting conden-' sate, forming a'liquid columnlof collected condensate, completely separating the gas spaces of different parts and establishing a pressure differential therebetween due to the forming of such liquid column, and modifying the behavior of a gilid in the system due to such pressure difleren al.

24. In the art of refrigeration as set forth in' claim 28, in which the behavior of a gaseous fluid/ circulating in the system is modified due to the pressure differential established between co pletely seted gas spaces of diflerent parts.

25. In the art of refrigeration with the aid of a system having a number of parts including an evaporator, an absorber and a generator interconnected for circulation of refrigerant and'absorption solution and employing an inert gas for maintaining the same'total ure in such parts during normal operation of the system, the inert; gas circulating in a circuitjincluding the evaporaior and the absorber, theimprovbment-wliiehcomprises collecting condensaiaiong a liquid column of collected condensate, compiteiy separating the gas spaces of difierent parts and establishing a pressure differential therebetween due to the forming of such liquid column, and modifying the behavior of the inert gas circulating in its circuit due to such pressure difierential.

26. In the art of refrigeration as set forth in claim 25, in which the circulation of inert gas in its circuit is reduced due to said pressure differential.

27. In the art of refrigeration as set forth in claim 25, in which the direction of flow of the inert gas through the evaporator is reversed due tosaid pressure differential.

28. In the art of refrigeration as set forth in claim 25, in which the direction of the flow of the inert gas through the evaporator is changed due to such pressure differential without changing the direction of flow of the inert gas through the absorber.

29. In the art of refrigeration with the aid of a system having a number of parts including an evaporator, an absorber and a generator interconnected for circulation of refrigerant and absorption solution and employing an inert gas for maintaining the same total pressure in such parts during normal operation of the system, the improvement which comprises collecting refrigerant fluid in liquid phase upon increase in load, forming' a liquid column of the collected refrigerant, completely separating the gas spaces of different parts and establishing a pressure variation therebetween due to the forming of such liquid column, and modifying the behavior of a fluid in the system due to such pressure variation.

'30. A refrigeration system containing an inert gas comprising a plurality of parts including a generator, an evaporator and an absorber interconnected for circulation of refrigerant and absorption liquid, the inert gas maintaining the same total pressure in the system and the gas spaces of different parts being in open communication with each other during normal operation of the system, means providing a. place for accumulating liquid upon increase in load, and structure to completely separate the gas spaces of said different parts responsive to said accumulation of liquid for changing the level of liquid in the system, said structure including means to modify the behavior of a fluid in the system responsive to such change in.level of liquid.

31. A refrigeration system as set forth in claim 30, in which said means for accumulating liquid includes a pressure vessel in which refrigerant vapor is liquefied upon increase in load.

SIGURD MA'I'I'IAS BACKSTRGM.

(References on following page) Number Name Date REFERENCES CITED 1,976,202 Thomas Oct. 9, 1934 The following references are of record in the 2,035,499 Nelson Mar. 31, 1936 file of this patent: 2,178,603 Nelson Nov. '7, 1939 5 2,181,528 Widell Nov. 28, 1939 UNHED STAIES PAIENIS 2,252,791 Ullstrand Aug. 19,1941 Number Name Date 2,282,684 Taylor May 12, 1942 1,846,626 Altenklrch Feb. 2 1932 2,306,199 Ullstrand Dec. 22, 1942 1,925,361 Altenkirch Sept. 5, 1933 1,930,671 Altenkirch 001;. 1'7 1933 

